The most common infections among injection drug users (IDUs) in the United States are caused by the hepatitis viruses. The prevalence and incidence of hepatitis B infections remain high despite the availability for more than two decades of an effective vaccine against hepatitis B. If we can successfully target IDUs and get them to complete the three-dose vaccination schedule, we may be able to protect IDUs from and decrease the national burden of hepatitis B infection. Preliminary data have identified three steps for achieving this goal: (1) relying on institutions that IDUs trust such as syringe exchange programs (SEPs), (2) accelerating the schedule for immunizing IDUs, (3) offering financial incentives to increase the likelihood that IDUs will return to receive all three doses. Incorporating these three steps, we are proposing a randomized trial of hepatitis B vaccination, with the specific aims: 1) To randomize study participants to compare the efficacy of the standard hepatitis B vaccination schedule (0, 1, and 6 months) to an accelerated schedule (0, 1, and 2 months); 2) To determine the extent to which SEP customers as compared to non-customers complete the hepatitis B vaccination series when the SEP advertises vaccine availability; 3) To determine the associations of demographic factors, hepatitis knowledge, health-seeking beliefs and perceptions, behavioral factors, and participant payment with vaccination completion; and 4) To estimate the costs and potential financial savings accruing from such a campaign. This study will be conducted in collaboration with the SEPs in Chicago, IL and Hartford CT by a multidisciplinary team that includes an epidemiologist, a biostatistician, a medical anthropologist, a bioethicist, a health economist, a health psychologist, and two physicians. [unreadable] [unreadable]